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Vacuum Tube SPICE Models
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Old 11th September 2021, 12:24 PM   #3081
prazza1 is offline prazza1  France
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Saw, thanks.
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Old 11th September 2021, 12:31 PM   #3082
OldHector is offline OldHector  Sweden
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Join Date: Jun 2018
Location: Täby, Sweden
I have been trying to get to grips with modelling the Tubelab SPP in LtSpice so that I can investigate how the simulation differs for an EL86 version. I am trying to add negative feedback, and I'd like to see how the operating points are affected by different values of the feedback resistor from the OPT secondary.

In order to do that, I have had to better understand how transformer models work, and I have also tried to derive a model for the Toroidy TTG-EL84PP, which looks to be quite different to the theoretical model I have in my simulation today.

Here is my test file for the Toroidy OPT, added to another simulation I sourced somewhere, and can't remember. I have had to get a better understanding of how the different windings are coupled, and calculate the inductances of each section.

In my näive view, the Toroidy should have the same power output as the theoretical one. With 300V p-p on the primary, the theoretical gives 25v p-p, so power output on the 16ohm tap should be ((25/1.4)^2)/16 = approx 20W, which is OK.

The Toroidy model only has 10V p-p. It has a primary inductance of 500H instead of 72H of the theoretical OPT.

Is this to be expected?
Attached Files
File Type: asc trafo-test-pp-8000k-001.asc (8.6 KB, 12 views)
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Old 11th September 2021, 05:18 PM   #3083
Koonw is offline Koonw
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Join Date: Apr 2013
Total pri inductance is 520H based on your data.
4 ohm inductance ratio=8000/4=2000
sec 4 ohms inductance=520/2000=0.26

sec 8 ohms inductance=0.26/6=0.0433
sec 16 ohms inductance=0.26/3=0.0867
40% UL tap=150*0.4=60Vp

see attach for sec output voltage
Attached Images
File Type: png 8k toroidal ul xformer.png (96.3 KB, 90 views)

Last edited by Koonw; 11th September 2021 at 05:22 PM.
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Old 11th September 2021, 08:50 PM   #3084
euro21 is offline euro21  Hungary
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Vacuum Tube SPICE Models
Hi Koonw,

The standard deviation of the 300B models is large enough.
Attached Images
File Type: jpg 300B models deviation.jpg (115.7 KB, 86 views)
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Old 11th September 2021, 10:55 PM   #3085
OldHector is offline OldHector  Sweden
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Location: Täby, Sweden
Quote:
Originally Posted by Koonw View Post
Total pri inductance is 520H based on your data ...
Hi Koonw,

Many thanks for setting me straight! Another small step for me in the right direction.

I was wondering what the purpose was of the two 4K resistors? I presume I omit them when I connect the taps to anodes in the circuit.

Cheers, Richard

Last edited by OldHector; 11th September 2021 at 11:06 PM.
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Old 12th September 2021, 02:07 AM   #3086
Koonw is offline Koonw
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Join Date: Apr 2013
Yes, you're correct to omit them in actual circuit. The purpose of two 4k resistors is chosen so they represent the total effective OT pri Z raa (r anode to anode) is 2*4k=8k, for OT Z=4k, two 2k resistors are used and so on. You can test by measuring the voltage after the resistors with respect to ground, should be half of generator voltage.


In actual circuit resistor is represented by the tube resistance, that is if raa=8k, and OT Z=8k when sec is connected, you'll measure 1/2 voltage at plate top with respect to ground or full voltage swing across the 2 plate tops

Last edited by Koonw; 12th September 2021 at 02:19 AM.
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Old 12th September 2021, 06:20 AM   #3087
Koonw is offline Koonw
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Join Date: Apr 2013
I have put together all the 300b models in one lib and each model is labeled using number rather than char. so can use ".step param tube list 1 2 4.." or just "param tube =7" will pick up 300b_we model.
The will make it possible for instant comparing various params like power dissipation, current, ouput and distortion etc.
Model naming as follow:-

1-EH
2-ER
3-FM
4-JJ
5-KR
6-PS
7-WE
8-GV
Attached Images
File Type: png 300b char comparing.png (74.7 KB, 78 views)
Attached Files
File Type: asc trans 300b model.asc (1.9 KB, 9 views)
File Type: txt 300b.lib.txt (11.3 KB, 9 views)
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Old 12th September 2021, 11:02 AM   #3088
Koonw is offline Koonw
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STC 4300B model


Code:
**** 4300B ** Advanced Grid Current **********************************
* Created on 09/12/2021 00:06 using paint_kit.jar 3.1
* Model Paint Tools: Trace Tube Parameters over Plate Curves, Interactively
* Plate Curves image file: 4300B.GIF
* Data source link: http://tdsl.duncanamps.com/dcigna/tu...c/4300b-3h.gif
*----------------------------------------------------------------------------------
.SUBCKT 300B-GD 1 2 3 ; Plate Grid Cathode
+ PARAMS: CCG=8.5P  CGP=7.5P CCP=11P 
+ MU=3.931 KG1=2763.1 KP=52.17 KVB=812.4 VCT=2.099 EX=1.534 
+ VGOFF=2 IGA=0.001 IGB=0.3 IGC=8 IGEX=1.6 
* Vp_MAX=650 Ip_MAX=100 Vg_step=20 Vg_start=0 Vg_count=11
* Rp=4000 Vg_ac=55 P_max=40 Vg_qui=-48 Vp_qui=300
* X_MIN=48 Y_MIN=26 X_SIZE=818 Y_SIZE=621 FSZ_X=1296 FSZ_Y=736 XYGrid=false
* showLoadLine=n showIp=y isDHT=n isPP=n isAsymPP=n showDissipLimit=y 
* showIg1=y gridLevel2=y isInputSnapped=n  
* XYProjections=n harmonicPlot=n dissipPlot=n 
*----------------------------------------------------------------------------------
E1 7 0 VALUE={V(1,3)/KP*LOG(1+EXP(KP*(1/MU+(VCT+V(2,3))/SQRT(KVB+V(1,3)*V(1,3)))))} 
RE1 7 0 1G  ; TO AVOID FLOATING NODES
G1 1 3 VALUE={(PWR(V(7),EX)+PWRS(V(7),EX))/KG1} 
RCP 1 3 1G   ; TO AVOID FLOATING NODES
C1 2 3 {CCG} ; CATHODE-GRID 
C2 2 1 {CGP} ; GRID=PLATE 
C3 1 3 {CCP} ; CATHODE-PLATE 
RE2 2 0 1G 
EGC 8 0 VALUE={V(2,3)-VGOFF} ; POSITIVE GRID THRESHOLD
GG 2 3 VALUE={(IGA+IGB/(IGC+V(1,3)))*(MU/KG1)*(PWR(V(8),IGEX)+PWRS(V(8),IGEX))}
.ENDS 
*$
Attached Images
File Type: jpg 300B-GD paint.jpg (380.0 KB, 65 views)
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Old 12th September 2021, 11:24 AM   #3089
Koonw is offline Koonw
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Join Date: Apr 2013
This sim is taken a step further:
Each tube set to output 200Vp
Each tube is bias so Pdissp is about 32W
STC 4300B is added to the list.
Attached Images
File Type: png 300b char comparing 2.png (100.6 KB, 68 views)
Attached Files
File Type: asc trans 300b model 3.asc (2.7 KB, 9 views)
File Type: txt 300b2.lib.txt (12.3 KB, 7 views)
File Type: txt trans 300b model 3.log..txt (7.2 KB, 8 views)

Last edited by Koonw; 12th September 2021 at 11:28 AM.
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Old 12th September 2021, 03:58 PM   #3090
Koonw is offline Koonw
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Join Date: Apr 2013
Total harmonic distortion (Thd) comparison of 300b's model with 3k5 and 5k OT.
Attached Images
File Type: png 300b char comparing 3k5 FFT-1.png (175.3 KB, 32 views)
File Type: png 300b char comparing 5k FFT-1.png (80.8 KB, 25 views)

Last edited by Koonw; 12th September 2021 at 04:04 PM.
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